Bifenthrin is a pyrethroid insecticide used against the red imported fire ant. It had a high toxicity to aquatic organisms. It is also used for the control of aphids, worms, ants, gnats, moths, beetles, grasshoppers, mites, midges, spiders, ticks, yellow jackets, maggots, thrips, caterpillars, flies, and fleas (EPA). It is often used in orchards, nurseries, and homes. It is extensively used on some crops including corn. Pesticide formulations containing bifenthrin were withdrawn from use in European Union in 2009; however, bifenthrin insecticide was reapproved for use in European Union in 2012. There have been established an acute and chronic reference dose (RfD) for bifenthrin, based on animal studies. The reference dose resembles the estimated quantity of a chemical to which a person could be exposed to every day (or a one-time exposure for the acute RfD) without any appreciable risk of adverse health effects. The acute reference dose (RfD) for bifenthrin is 0.328 mg/kg bodyweight/day. The chronic reference dose (RfD) for bifenthrin is 0.013 mg/kg bodyweight/day. Concentrations up to 10-4 M do not induce toxic effects. Commercially available bifenthrin, however, can induce toxic effects in those concentrations, because the chemicals added to the product, which for instance improve the sustainability, either potentiate bifenthrin or are themselves toxic. Symptoms of excessive exposure to bifenthrin are nausea, headaches, hypersensitivity to touch and sound and irritation of the skin and the eyes.
Bifenthrin has been formulated in variety of ways which have low concentration of bifenthrin. Most of the formulations exhibit toxicity e.g. dermal toxicity or inhalation toxicity, and contact irritation or eye irritancy, if higher concentrations of bifenthrin are used in the formulation. However, the low bifenthrin content formulations become economically unviable in agricultural applications.
Bifenthrin formulations are at times applied to the soil in fields in the form of injections. The soil applied insecticide formulation is tank mixed with a fertilizer for a combined and easier application. However when the insecticide formulation is combined with liquid fertilizer, there is a problem with reduced physical stability of the mixture due to the presence of other ingredients in the insecticide formulation like surfactants, wetting agents, viscosity modifiers and other auxiliaries, which results in degradation of the mixture leading to phase separation, creaming, flocculation, turbidity, caking, and poor performance. It is desirable that such formulations need be compatible with other formulations such as liquid fertilizers which are applied simultaneously or are mixed with the insecticide formulation prior to application.
Although various formulations of bifenthrin are available commercially, there is a need to develop a bifenthrin formulation which has reduced toxicity and good liquid fertilizer compatibility, and is environment friendly.
The present invention addresses the above mentioned drawbacks of previously known and used bifenthrin formulations.